The present invention relates to sootblowers for rotary regenerative air preheaters and particularly to a swing-arm cleaner moving across the air preheater rotor which is adapted to clean with different mediums and at various pressures.
Soot or other related materials from flue gases tend to deposit over a period of time on the heat transfer surface of the rotor of a rotary regenerative air preheater. As these deposits build up, the flow paths for the air and flue gas become blocked and the heat transfer capacity is reduced. Therefore, it is common for these air preheaters to include devices for blowing air or steam at high velocities into the rotor to dislodge the deposits.
The typical cleaner or sootblower for a rotary regenerative air preheater employs a swing-arm mounted for rotation through a set angle or arc with one or more nozzles at the end which blow the sootblowing medium (air or steam) into the rotor as the rotor turns and as the swing-arm rotates through the arc. The sootblower is normally mounted on the cold end of the rotor, which is the outlet end for the flue gas, but may be mounted as required in either the air or gas duct and either on the cold end or the hot end.
The current prior art sootblowers employ a swing-arm mechanism which is swept across the air preheater rotor at a selectable constant angular velocity from the beginning to the end of the sweep. These swing-arm sootblowers have a constant speed drive assembly, using a motor whose speed is adjustable, adapted to rotate a drive sprocket, preferably with a torque-limiter clutch. The drive sprocket is positively connected to a driven sprocket, such as by a drive chain with the driven sprocket being mounted on a swivel shaft to which the sootblower arm or lance is attached. Means such as limit switches terminate the swivel of the sootblower arm at the ends of its arc of travel toward the center and outside periphery of the rotor and turn off the sootblowing medium. These constant speed swing-arm sootblowers spread the energy of the sootblowing medium evenly over the radius of the rotor, conserve on the use of the sootblowing medium and reduce wear caused by excess medium in certain areas. For a disclosure of such swing-arm sootblowers, see U.S. Pat. No. 5,626,184.
Present sootblower designs have an arm or lance with a single conduit for supplying the cleaning medium to the nozzle at the end of the arm. Although there may be provisions for switching between several cleaning mediums, such as air, steam or water, these cleaning mediums are all at low pressures, i.e., below about 1000 psig. This low pressure washing is not able to effectively clean hardened particulate material that accumulates over the normal operational period of the air preheater. Therefore, it is necessary to periodically shut down the air preheater and use separate high pressure water washing equipment. This process is time consuming, increases cost and increases down time.